1. Brief Description of the Field of the Invention
The present invention relates to novel organophilic clays which are dispersible in non-aqueous fluids to provide rheological properties to such fluids. The invention also pertains to a process for preparing these organophilic clays using multiple cations such as quaternary ammonium compounds, and one or more organic anions. The invention includes non-aqueous fluid compositions including such organophilic clays as rheological additives.
2. Description of the Prior Art
It has long been known that organophilic clays can be used to thicken a variety of organic compositions. Such organophilic clays are prepared by the reaction of an organic cation with a clay in various methods known in the art. If the organic cation contains at least one alkyl group containing at least 8 to 10 carbon atoms, then such organoclays have the property of increasing viscosity in organic liquids and thus providing rheological properties to a wide variety of such liquids including paints, coatings, adhesives and similar products.
It is also well known that such organoclays may function to thicken polar or non-polar solvents, depending on the substituents on the organic salt. J. W. Jordan, in "Proceedings of the 10th National Conference on Clays and Clay Minerals" (1963), discusses a wide range of applications of organoclays from high polarity liquids to low polarity liquids.
The efficiency of organophilic clays in non-aqueous systems can be further improved by adding a low molecular weight polar organic material to the composition. Such polar organic materials have been called dispersants, dispersion aids, solvating agents and the like. See, for example, U.S. Pat. Nos. 2,677,661; 2,704,276; 2,833,720; 2,879,229; and 3,294,683. The most efficient polar materials for use as such have been found to be low molecular weight alcohols and ketones, particularly methanol and acetone.
Furthermore, U.S. Pat. Nos. 3,977,894; 4,382,868; 4,464,274; and 4,664,820 describe the preparation of preactivated organophilic clay gellants that are used to thicken organic compositions wherein the activators are admixed with the organophilic clay.
More recently, organophilic clay gellants have been developed which are the reaction products of smectite-type clays having a cation exchange capacity with certain organic cations or organic cations and organic anion combinations. These gellants have the advantage of being effectively dispersible in particular organic compositions without the need for a dispersion aid under normal shear conditions. Illustrative patents which describe such improved organophilic clay gellants are U.S. Patent Nos. 4,105,578; 4,208,218; 4,287,086; 4,391,637, 4,410,364; 4,412,018; 4,434,075; 4,434,076; 4,450,095; and 4,517,112.
One way to enhance the gelling and dispersing efficiency of an organophilic clay is to replace some of the hydrophobic side groups attached to the organic cation with hydroxyalkyl groups. In these groups, the hydroxyl group is attached to any carbon atom on an aliphatic radical, except for the carbon atom adjacent to the positively charged atom as disclosed in U.S. Pat. No. 4,434,076.
To further impart improved gelling properties, the groups attached to the organic salt may be replaced by a mono- or polyhydroxylated group. Modified organophilic clays containing these compounds swell and gel in organic liquids without the need for polar dispersion additives. For example, European Patent Application 0,133,071 describes modified organophilic clays resulting from the combination of a smectite clay, a quaternary ammonium salt having a long hydrocarbon chain, and a mono- or polyhydroxylated nitrogeneous surfactant. The mono- and polyhydroxylated nitrogeneous organic surfactants used in the disclosed formulations are ethoxylated amines and alkoxylated quaternary ammonium salts having long hydrocarbon chains, such as (tallow alkyl)- or di(tallow alkyl)-(methyl or benzyl) ammonium salts.
Further increases in the amount of alkoxylated groups, however, result in clay compositions that impart gelling properties to aqueous systems rather than to non-aqueous systems. For example, U.S. Pat. No. 4,677,158 describes a reaction product of a smectite clay and a quaternary ammonium compound that is used as a thickener for aqueous suspensions, particularly water based latex paints and caulks. The disclosed quaternary ammonium compound is said to consist of a nitrogen atom bonded to separate carbon chains where one chain can be a methyl group or alkyl group containing 10 to 20 carbon atoms, and the second chain is an alkyl group containing from 10 to 22 carbon atoms or a polyoxyethylene chain, The third and fourth chains are polyoxyethylene chains such that the total number of ethylene oxide units is from 5 to 200 moles,
The disadvantages of most existing organoclay compositions for non-aqueous systems are that (a) relatively large amounts of the organoclay compositions are needed to impart the required viscosity; (b) polar activators are required in many cases to enhance their gelling properties; and (c) the organoclays are limited to either polar or non-polar systems depending upon their organic content.